Then there is R. Lee in his book on modern reloading, he ran primers across a chronograph, 700 fps +/- a few or about 225 mph. And then there is the primer, bullet case and no powder, the primer alone can drive the bullet into the barrel/forcing cone.

F. Guffey

I am not sure what point you are making?

As far as a forcing cone or barrel is concerned, the evidence suggests that there was no firearm involved. There are no striations on the bullet's side and the condition of the case suggest no chamber was involved, or if there was one, said chamber ruptured very quickly.

700 fps is approximately 477 mph.

I can't get a primer to run at all. How did he do it? Their little legs are so short! I can get them to roll (whenever I drop one, it rolls away REAL FAST, but running is out of the question).